This disclosure relates to centering a steering rack associated with a power steering assembly for an automotive vehicle. More particularly, this disclosure relates to centering of the steering rack at the factory and eliminates use of separate, external power equipment for adjusting a position of the steering rack during the centering process.
Electric power steering (EPS) systems are becoming more widely used and replacing hydraulic power steering systems in automotive vehicles. As part of the EPS, an electric motor is mounted on the steering column or the gearbox and an angular position sensor (resolver) is mounted adjacent to the motor with the primary purpose of allowing brushless motor commutation. An electronic control unit (ECU) or controller on the automotive vehicle operatively receives input data relating to, for example, an angular position and speed of the motor, vehicle speed, pinion torque, etc. The controller processes this data and communicates with or commands the electric motor to provide a desired assistance to the steering system. A number of advantages are associated with EPS systems including decreased weight, increased engine power, no fluid leaks or pump noise, improvements in handling and steering, and an increase in fuel economy. This list of advantages is merely representative and not deemed to be limiting.
As is the case with hydraulic power steering systems, before a steering wheel is installed at the factory in an EPS system, the center of the steering rack must be located. This ensures that the steering wheel angle to each side of the center is roughly equal, i.e., the wheels of the car can be turned substantially the same amount in the right-hand and left-hand turn directions. Currently, an external, powered rotary device is temporarily connected to the automotive vehicle during the manufacturing process and, more specifically, is connected to an input shaft of a steering column. The powered rotary device strokes the steering gearbox or rack to each side (or end) of the rack to find a total stroke, and then finds the center of the rack by identifying the middle between the ends. A mark is oftentimes made for subsequent, accurate installation of the steering wheel or, once the center is located, the steering column is held in place relative to the rack until the steering wheel is mounted and secured in position.
This known arrangement requires the factory to employ special equipment to center the gearbox rack. In addition to the capital costs associated with this specialized centering equipment, there are additional costs associated with maintenance of the specialized centering equipment. Further, this specialized centering equipment has manpower levels measured, for example, in terms of the time associated with the steering centering process. More specifically, there is an average total time associated with temporarily mounting the centering equipment to the automotive vehicle, operating or running the gearbox or rack centering equipment, and subsequently removing the centering equipment from the vehicle.
A need exists that reduces cost, assembly time, and meets or exceeds the associated conventional equipment and process for factory centering of the steering rack.